Serena Williams has revealed she is 20-weeks pregnant with her first child .

The world No 2 has not played since the Australian Open in January where she beat sister Venus 6-4, 6-4 for her 23rd grand slam title. Last month the American pulled out of Indian Wells and Miami Open citing a knee injury.

The tennis superstar will not play again in 2017 but will return to the tour in 2018, her spokeswoman said.

Kelly Bush Novak told that Williams "definitely" would not be able to play again this year but "looks forward to returning in 2018."